BOxMERANG. 117 



B C = 3 inches. Thus constructed, the centre 

 of gravity will fall exactly on the edge of its 

 concave surface at C. When used as an offen- 

 sive weapon, it is usually thrown with the convex 

 side outwards ; but when intended to return, it 

 is held in the reverse position ; although it will 

 probably act in either direction, if properly 

 managed. 



" For the latter purpose, however, it should 

 be thrown from the hand at a considerable ele- 

 vation (45°) with a sudden jerk, so as to com- 

 bine with the projectile force a rapid rotation 

 round its centre of gravity. The rotation acts 

 constantly in opposition to its line of flight ; so 

 that if a similar rotation could be communicated 

 without any projectile force, the instrument 

 would move backwards : now, as the force with 

 which it is thrown is constantly diminishing 

 while the rotation continues, it must always 

 arrive at a certain point where these opposite 



